Shallow coastal environments, particularly sandy tidal basins, are com-ing under increasing pressures due to human development and a changingclimate. This has led to a demand for long-term predictions of sedimenttransport using deterministic, process-based coastal area models. Due tocontinually growing model complexity this has involved an increased compu-tational cost, resulting in the development of a variety of methods to speedup computation time while having a minimal impact on model accuracy. Thepresent body of work introduces one of the most popular speed-up methods,the Morphological Factor (MF) method, to theTELEMAChydro-informaticsmodelling system.Using the depth-averaged, shallow water hydrodynamic and sedimenttransport models,TELEMAC 2DandSISYPHErespectively, a long-term simu-lation of a schematised tidal basin system is conducted. From infinitesimalperturbations to an initially flat bed a highly regular morphological patternis seen to evolve spontaneously through the processes of self-organisation,subsequently forming the basis of a dynamic and intricate tidal channel net-work. Due to the time-stepping nature of the model, the initial pattern isresponsible for all future simulated morphologies, yet this linkage has re-ceived little attention in the literature. Further simulations identify the firststages of the bed pattern as a dissipative structure, requiring more energyfrom the flow to create and maintain than the initial flat bed itself, which iscontradictory to a linear, mechanistic treatment of the system.
Dunes, sedimentary bed forms ubiquitous to the coastal zone, have a sig-nificant impact on flow speed (and therefore sediment transport and morpho-logical change) through the roughness created by their geometry. Althoughthe effects of dune-scale roughness on the flow and sediment transport arediscussed in the literature the impact of a time-evolving roughness feedbackbetween the bed and the flow in a coupled morphological model is poorlyunderstood. In the present work a roughness feedback mechanism is imple-mented inTELEMAC 2DandSISYPHEand the predicted roughness is validated in a model of the Dyfi Estuary, Wales, using the results of a swathe sonarbathymetric survey. The model results show very promising agreement withthe data given the simplifying assumptions made. The tidal residual sedi-ment transport rate in a simplified model case is shown to not only change inmagnitude, but also in sign, between cases with and without bed roughnessfeedback, showing that the method has significant implications for long-termmorphological change.Deterministic models are frequently used to predict changes in the long-term, yet their mechanistic nature forces the outcome to be sensitive toinitial conditions. Natural systems, however, contain both deterministic andprobabilistic elements that create structures and patterns at a variety of dif-ferent scales, many of which can be captured by process based models suchasTELEMAC 2DandSISYPHE. In the present work a stochastic, infinitesi-mal perturbation is introduced to three otherwise identical long-term modelsimulations, resulting in system divergence through three independent mor-phological system parameters. The sensitivity to initial conditions and theimportant role of self-organisation are seen to produce dynamic morphologi-cal behaviour that is inherent to the theory of open, dissipative systems.